Conor McGregor suffered a broken leg in another crushing defeat to Dustin Poirier at the T-Mobile Arena in Las Vegas, with the fight stopped by doctors at the end of the first round.
As a thrilling first five-minute frame drew to a close, both fighters were still trying to land as McGregor stumbled backwards, trapping his foot under himself and breaking his leg.
Medics were immediately called into the Octagon and it was clear that McGregor could not continue and the referee Herb Dean declared a stop to the bout on the instructions of the doctor.
McGregor, who had not won at lightweight since beating Eddie Alvarez to claim the title in 2016, was knocked out by Poirier for the first time in his career when the two met in Abu Dhabi in January.
The fight started brightly for the former two division champion, landing several hard shots on the American, and even stinging Poirier with a beautiful left hand.
But Poirier remained calm and midway through the round he nailed McGregor with a heavy combination and forced the fight to the mat.
From there, Poirier pounded away on the 32-year-old, mauling McGregor with heavy shots, although the Irishman kept his composure and looked set to survive the onslaught.
As the round drew to a close, Poirier let McGregor up and the two exchanged hands only for McGregor to fall to the mat in agony.
As the siren went to complete the round, it became obvious that McGregor was severely compromised and wouldn't be able to continue.
Under the doctor's advice, referee Herb Dean called a stop to the fight and declared Poirier the winner.
McGregor had to leave the arena on a stretcher
After the bout, Poirier took exception to McGregor's trash talk heading into the fight, as the former UFC lightweight and featherweight champ claimed he'd murder Poirier and made objectionable comments about his wife.
"He was telling me he was going to kill me, murder me, you don't talk like that, man," said Poirier, who won for the eighth time in his past nine fights. "The guy's a dirtbag. Karma's not a b----, she's a mirror."
The evening's co-feature bout can best be described as a tactical affair, as Brazil's Gilbert Burns took a battle of former welterweight title challengers over South Carolina's Stephen Thompson. Burns (20-4) used his grappling game to keep Thompson (16-5-1) from implementing his kickboxing game, which was good for a unanimous decision on straight 29-28 scores.
The crowd by and large was dissatisfied with the lack of action in the bout, which came one fight after a wild one tore down the house.
Australian heavyweight Tai Tuivasa (13-3) needed just 67 seconds to score a violent knockout of former NFL All-Pro and convicted domestic abuser Greg Hardy (7-4). A huge right to the jaw did the job.
Reuters / Newshub